The effect of litter accumulation on vegetation dynamics after grassland restoration by sowing
Abstract
The relationship between litter accumulation, herbaceous phytomass and species richness was studied on ex-alfalfa fields restored with low diversity seed mixtures. The following hypotheses were tested: (i) Accumulated litter is higher in the restored grasslands than in the reference ones. (ii) With increasing amounts of litter, species richness decreases. (iii) The phytomass of herbaceous species is negatively correlated with the amount of litter and graminoid phytomass. In 10 stands (4 sown with Festuca pseudovina and Poa angustifolia and 6 sown with Festuca rupicola, Poa angustifolia and Bromus inermis) aboveground phytomass samples were taken in June 2006, 2007 and 2008. In the first year after sowing, the vegetation was dominated by annual weedy species. Weedy assemblages were replaced by communities dominated by clonal grasses in the following vegetation period. In the second year after sowing, significantly lower herbaceous phytomass was sampled, while the amount of litter were increased significantly. The amount of the sown graminoid phytomass was increasing from year to year. We found strong negative correlation between litter and herbaceous phytomass. Our results suggest that litter accumulation and the competition of perennial graminoid species can negatively affect the germination, survival and colonisation of herbaceous species. Sustaining management by mowing or extensive grazing can be an appropriate tool to reduce the amount of accumulated litter.
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